In these two cases of use, said shell must have structural qualities of rigidity and resistance to the impacts and indentations to which such equipment may be subjected, and also it must be made with precision so as to adapt perfectly to the dimensions of the object and/or components.
Other applications of the method according to the invention may be considered particularly in the making of a half shell designed for luggage items in order to make small cases, suitcases or protective cases.
In these applications as in the previous ones, the constraints relating to mechanical resistance and precision must be addressed, while keeping the objects lightweight.
These consumer goods are produced in very large runs and are subject to seasonality and decoration constraints to adapt them to the tastes of consumers or the distinctive colors and signs of their distributors. These products are intended for the general public and for equipment that is frequently renewed, and must allow advantageous recycling or, at least, have a low environmental impact.
To that end, it is advantageous to make such a part, particularly a half shell for a tablet PC, in stratified composite material comprising a thermoplastic matrix and a continuous fibrous reinforcement, wherein said fibrous reinforcement mostly comprises natural fibers of plant origin. The part is made up of a plastic matrix and continuous fibrous reinforcement, and is both lightweight and particularly strong. The thermoplastic nature of the matrix makes it easy to recycle, just as the nature of the reinforcing fibers limits its environmental impact in terms of the making of the raw material and its recycling or disposal as waste.
However, because the reinforcement is made up of continuous fibers, such a part cannot be made using the plastic injection methods that are generally considered for this type of mass manufacturing. Similarly, a method for stamping pre-consolidated thermoplastic blanks such as that described in document FR-A-2922276 is not applicable, because pre-heating the blank before stamping to a temperature that is sufficient to allow the relative sliding of the fibers in the non-developable areas, thanks to the fluidity of the resin, would lead to a risk of burning the fibers when the fibers are natural, particularly when they are of plant origin. The method described in document FR-A-2922276 is thus more particularly adapted to the manufacturing of a part where the fibrous reinforcement takes the form of carbon, glass or aramid fibers that are not liable to be affected by such burning phenomena at the melting temperature of the resin. Besides, the humidity content of natural fibers may be greater than 10%, which humidity is liable to be changed into water vapor during the hot stamping operation and could lead to quality defects.
The method described in document FR-B-2882682 solves the problem of the flammability of natural fibers by carrying out the forming process using a vacuum bag device. That method does not make it possible to obtain tight non-developable shapes such as corner fittings at the trihedral connections. That is because this method, which does not make it possible to put the textiles under tension, leads to the formation of creases and/or wrinkling in or near the non-developable areas. Besides, this method for forming and compacting using a membrane or bag does not allow high production rates that are suitable for the runs concerned by the intended applications. Thus, in the prior art, there is no method suitable for making such a part.